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Overview

The 34675 is a high input voltage Li-Ion battery charger with a 4.85 V/10 mA linear regulator. The high input voltage, up to 28 V, eliminates the input over-voltage protection circuit required in handheld devices such as cell phones, Bluetooth accessories, and portable media players. The 4.85 V linear regulator is capable of 10 mA output current, and can be used to directly power a sub-system such as USB transceivers.

The charge cycle of the MC34675 includes trickle , constant-current (CC), and constant-voltage (CV) charge modes. The CC-mode current is programmable up to 1A with an external resistor. The constant voltage is fixed at 4.2 V with 0.7% accuracy over a -40 °C to 85 °C temperature range. The trickle-mode current is pre-set to 20% of the CC-mode current, when the battery voltage is lower than the trickle-mode threshold. The end-of-charge (EOC) current threshold is pre-set to 10% of the CC-mode current to save the board space and cost.

A charge-current thermal-foldback feature limits the charge current when the IC internal temperature rises to the pre-set threshold of 120 °C. The MC34675 also protects the system with its input over-voltage protection (OVP) feature. Two indication pins (PPR and CHG) can be simply interfaced to a microprocessor or LEDs. When no power supply is connected, or when disabled, the charger draws less than 1.0 µA leakage current from the battery.